It's my favourite F cabin by a country mile - if travelling alone, I'd recommend 2K or 4F (especially 4F). As there is a curtained-off crew rest area where 4K would be, nobody walks past your seats other than cabin crew as there is nowhere to go heading to the back of the cabin.

For me, the most private F seat on BA (I've done 380s, 777 12F, 14F and 17F, 747s but not the 787 in F). Admittedly the IFE isn't so great, but I'd still take the 12F cabin given the choice.

Yes, as per your point above, it's guaranteed to be the new (blue-seat) F